To understand protein metabolism in chronic renal failure patients (CRF pts), we measured measured whole body leucine flux during primed-constant infusion of 13C-leucine in the postabsorptive state in 9 CRF pts on three occasions: before dialysis and pts were acidotic (A), before dialysis with bicarbonate supplement and pts were non-acidotic (NA), and 6-8 weeks after initiation of dialysis (D). Protein intake was 0.9 +/- 0.15 g/kg/day in all periods. Plasma 13C-leucine and 13C-KIC (alpha-keto-isocaproate) were measured by gas chromatography/ mass spectrometry, and breath 13CO2, isotope ratio spectrometry. The data indicate that acidosis led to increased F13CO2 production and leucine oxidation. While uremia per se did not increase protein degradation, dialysis did improve protein anabolism as evidenced by a rise in leucine flux and an increase in protein synthesis.These findings underscore the importance of bicarbonate supplement and dialysis treatment in maintaining nutrition of CRF pts.